(a) Field of the Invention
The invention relates to a protection structure of a ceramic resistor heating module, and more particularly, to a protection structure of a heating module that utilizes ceramic resistors having a positive temperature coefficient as heating elements thereof. The module comprises ceramic resistor heating elements, and dielectric plates and cooling fins at two sides thereof. Insulation layers are adopted to achieve all-round protection, thereby allowing the invention to be applied in hazardous environments.
(b) Description of the Prior Art
Referring to FIG. 1, a ceramic resistor heating module 1 comprises ceramic heating elements 2, and cooling fins 3 joined at outer sides of dielectric plates 4 and joining plates 40 at two sides.
Each the dielectric plate 4 has one end thereof formed with an electricity conducting terminal 41, and two ends thereof sealed by sealing covers 11 and 12. A clamp board 14 at assembled to each side of the module 1, with an elastic device 13 pressed and joined in between.
The assembly according to the aforesaid description is frequently used, wherein various members including the ceramic heating elements 2 and the dielectric plates 4, the joining plates 40 and the cooling fins, are pressed and clamped using the elastic devices 13 and the clamp plates 14 from outer sides, followed by sealing using the sealing covers 11 and 12, thereby forming a heating device.
Referring to FIG. 2 showing the prior heat dissipating module in another type of assembly, the heating elements 2 are similarly used, and the dielectric plates 4 are laterally disposed to join with the cooling fins 3.
Referring to FIG. 3, adhesive 5 is applied between the cooling fin 3 and the dielectric plate 4 to assemble the structure. Similarly, the heating elements 2 are also assembled using adhesion means to further form a heat dissipating module.
Referring to FIG. 4 showing another type of assembly means, fundamental parts are used to assemble the dielectric plate 4 and the cooling fin 3 through welding means, and then the dielectric plate 4 and the heating element 2 are joined using any methods.
Referring to FIG. 5 showing the aforesaid welding method, between a lower side of the cooling fin 3 and one side of the dielectric plate 4, a welding point 6 is set for welding to assemble the cooling fin 3 with the dielectric plate 4.
Similarly, the heating element 2 is assembled with the dielectric plate 4 using any methods.
Apart from heat conducting effects by discharging heat energy of the heating element 2 to an exterior, the cooling fins 3 and the dielectric plates 4 are more targeted at conducting electricity. Referring to FIG. 1, the electricity conducting terminal 41 conducts electricity and provides the heating element 2 with electricity by conducting through a side of the heating element 2.
Besides the aforesaid assembly means as mechanical and elastic pressing or fastening as shown in FIG. 1, assembly is also accomplished by welding as shown in FIG. 5.
However, the heating modules formed according to the aforesaid assembly methods are incapable of withstanding wash tests by salty water. Salty water tests are for testing endurance of the heating modules against salt, acids and alkalis
The purpose of the above tests commonly used by the industrialists is to offer the heating elements with optimal physical property endurance and environment condition endurance when applied outdoors, especially when applied to automobile heating systems, so as to avoid loosening and deterioration. In the test, a liquid containing 5% of salt is used to continuously wash the heating module.
The aforesaid assembly methods includes a method used by German DBK Corporation to produce heating modules, which are tested by undergoing wash using water containing 5% of salt for 120 hours. The test results show that the heating modules fail to perform normal functions and become incapable of producing heat although overall structures of the heating modules remain intact. Heating modules assembled by adhesion, after undergoing wash tests with water containing 5% of salt for 120 hours, have loosening parts, with short circuits and sparkles resulted during the process. Therefore, for safety reasons, it is essential that the heating module be provided with an all-round protection structure, which is resistant against acids and alkalis or salt, so as to further insulate organic matters such as carbon monoxides or hydrogen oxides contained in moistures or air.